Thousands of teenagers are being exposed to graphic sexual material, violence, drug abuse and high levels of profanity on school-themed Facebook pages run by students.

Dedicated sites dubbed "OMG Confessions" or "memes" have become increasingly popular all over New Zealand.

The pages are set up anonymously - usually by a student from a particular school who invites pupils from that school to confess their secrets.

But the pages have quickly turned into forums for abuse and harassment, with teens posting offensive photos, descriptions of sexual encounters, drug-use on campus and naming and shaming peers.

The Weekend Herald found 55 schools in the Auckland and Northland region associated to such pages, and 26 linked by the student users to graphic sexual material, profanity, alcohol or drug-use at school or tormenting of other students.

Most of the pages set no boundaries. One site tells users: "Got some confessions? Big, small, dirty, innocent, lovey, whatever it is ...

send it in."

Another reads: "I am not responsible for all hateful material on this page. So send it all ... your confession 100 per cent anon."

And there is no holding back, with students abusing others and calling them sexual names.

On another page, a student at a top Auckland school goes into detail about a sexual encounter at a nearby golf course.

Teachers are also commented on. One page accuses a teacher of being "horny" in class; another says a named teacher left the school because he had an affair with a colleague.

Another page gives details about a group fight between students from two rival schools.

Internet safety group NetSafe said it had reached a desperation point with schools, which were trying to remove the pages because of the offensive material and the repercussions they were having to deal with, such as bullying at school.

Operations manager Lee Chisholm said NetSafe had been dealing with complaints about confession pages for the past six to eight months from schools, parents and students.

"Some of it is outright lies about other students. A lot of it is sexual and it can be about teachers as well as students.

"We have been reporting them on to Facebook at quite a high rate. Some days, I'll report three or four, sometimes just one. But yes, we've definitely had a spate of them."

More than 100 cyber experts are attending a NetSafe conference in Wellington next week to investigate issues of cyberbullying, online privacy, and human rights.

Social media expert Simon Young said much of the attraction for students sharing on such sites was the guaranteed anonymity and the idea that they could say anything they liked and not be caught.

"It's human nature. Sometimes when we're in a position of power and we're not very mature, we'll try to show that.

"It's power. That's the amazing thing about social media. It gives everybody with a computer a voice ... anyone can be a media person."

Mr Young said cyber-bullying had taken on a whole new level because of the confessions pages.

And the bullying had expanded on to the playground.

"People have always told stories about each other, and there's always been a dark side, but it's now much more public."

Schools are now making moves to introduce official Facebook pages to counter the negative confessions-type pages.

One school that had a confession page removed is Pakuranga College, in Auckland.

The school went to NetSafe for help a few months ago after a former student alerted staff about the content students were discussing on the page.

Associate principal Richard Dykes said what staff found was unbelievable.

A day after the school involved NetSafe, Facebook removed the page and the school started an investigation to trace the student who created it.

That was a few months ago and with the help of a group of student leaders, the school has set up an official Facebook page in a bid to encourage students to post positive things and take pride in their school.

Students are encouraged to send in photos of school trips and outings or good news about students, which are then posted online.

Its latest posting is a congratulatory message to this year's school dux.

Mr Dykes said: "If a student's achieved something and it's been in the (newspaper), for example, I'll take a screenshot and post it on the page.

"We've taken a really proactive stand against this for a couple of years now ... just because it is part of students' lives."